Flexible strand conveyor system with compensating spreader bar assembly



Nov. 28, 1961 R. F. LO PRESTI FLEXIBLE STRAND CONVEYOR SYSTEM WITHCOMPENSATING Filed Sept. 9, 1958 SPREADER BAR ASSEMBLY 2 Sheets-Sheet 1INVENTOR.

Roy F LoPresti BY mm 2 ATTORNEY Nov. 28, 1961 Filed Sept. 9, 1958 R. F.LO PRESTI FLEXIBLE STRAND CONVEYOR SYSTEM WITH COMPENSATING SPREADER BARASSEMBLY Fig. 2

2 Sheets-Sheet 2 INVENTOR.

Roy E LoPresii TTORNEV United States Patent FLEXIBLE STRAND CONVEYORSYSTEM WITH COMPENSATIN G SPREADER BAR ASSEMBLY Roy F. Lo Presti,Chicago, Ill., assignor to Goodman Manufacturing Company, Chicago, 111.,a corporation of Illinois Filed Sept. 9, 1958, Ser. No. 759,879 3Claims. (Cl. 198-184) This invention relates generally to conveyors andis particularly directed to means for maintaining the belt of a flexiblestrand conveyor centrally entrained along the roller assemblies of theconveyor under all load conditions.

Flexible strand conveyors of the type illustrated in the Craggs et al.Patent No. 2,773,257 are coming into widespread use due to their manyinherent desirable features including ruggedness, ease of assembly,accuracy of adjustment and low cost of installation, operation andinitial investment. In general, these conveyors are composed of a pairof generally parallel flexible strands, such as wire ropes or the like,trained along a course, such as a mine run, and are supported at spacedintervals by ground engaging supports. The supports may be connecteddirectly to the ground or to some other substantially rigid supportstructure, and may be spaced at intervals varying from 10 to feetdepending on a number of factors. Ten feet is a spacing commonly used inthe coal mining industry for example.

A plurality of roller assemblies are interposed between adjacent groundengaging supports which determine the nominal gauge of the conveyor andform a bed for the flexible conveying belt. These roller assemblies varywidely, but a typical assembly may comprise a center, primary belttraining roller pivotally connected to a pair of side or wing rollers.The wing rollers in turn are adapted to be connected to the flexiblestrands at their outer ends by means of clamps, or other suitablesecuring means.

In operation, a belt is trained along the roller assemblies and causedto run centered by means of preliminary adjustments. For example, if abelt tends to run high to one side, this tendency may be remedied bymerely canting the opposite end of the roller assembly back towards thedirection of travel. I

In this type of conveyor it is not absolutely essential that a groundengaging support be employed at the beginning and end of each spacedinterval. It is frequently suficient in coal mining applications forexample, to utilize support stands placed at 20 foot intervals. Rigidspreader bars located half way between supports may then be suspendedfrom the strands to maintain the proper strand spacing. The use ofspreader bars cutsthe cost of the final assembly considerably, since asupport stand is a more complex structure requiring additionalfabricating operations.

When spreader bars having a length substantially equal to the distancebetween suspension points (i.e., gauge) at the support stands areutilized, it not infrequently happens that rather erratic belt trainingresults follow due to the catenary sag of the strands. This inherentdownward droop of the strands is increased by the. weight of the rollerassemblies which also tend to pull the ropes closer together. The rollerassemblies farthest from the ground engaging supports will be lower thanthose next adjacent the supports. In a conveyor system having fourroller assemblies suspended from flexible strands 48 inches apartbetween a pair of ground engaging supports, there may be as much as aninch difference in height between the primary training rollers of theroller assemblies located midway between these supports and thoselocated adjacent the supports. Conventional spreader bars having a spanequal to the span between suspension points at the support standsmaintain substantially uniform spacing of the strands but do notcounteract the catenary sag.

These erratic results may be illustrated by the following example. Abelt may be trained with a load on it so that it runs straight down themiddle of the roller assemblies, but when the load is removed the beltmay run wildly off to one side or the other. This can easily occur whenthe rollers next adjacent the rigid ground engaging support structuresare cooked out of line, for example, to the right in the direction oftravel, and more remote roller assemblies are cocked out of line in theopposite direction. When the belt is loaded it will press firmly on allthe rollers and the detraining tendencies cancel one another. As soon asthe load is taken oil the belt, however, the belt rises and may besupported only by those roller assemblies next adjacent the groundengaging support structures. The left detraining tendency of the lowerroller assemblies is thereby removed and there is no counteractingforces preventing detraining of the belt to the right.

Accordingly, a primary object of the invention is the provision of meansfor maintaining the primary training rollers of a flexible strandconveyor system at substantially the same level.

Another object is the provision of means for maintaining good belttraining contact of roller assemblies under all load conditions.

Another object is the provision of means for increasing the belttraining efiect of a flexible strand conveyor by decreasing the includedangle between the center primary training roller and the wing rollers ofthe roller assemblies to thereby decrease the unsupported gap of beltbetween the center and wing rollers.

Another object is the provision of an elongated, substantially rigidspreader bar capable of being suspended from the flexible strands of aflexible strand conveyor and out of contact with the ground which willmaintain the level of the primary training roller of the rollerassemblies next adjacent it at a level substantially equal to the levelof the primary training rollers of roller assemblies next adjacent theground engaging support stands.

A further object is the provision of a conveyor system comprising a pairof flexible strands suspended between a pair of ground engaging supportstructures, a plurality of roller assemblies suspended from the strandsand a spreader bar assembly connected across the strands forcounteracting the catenary sag of the strands between the groundengaging supports to maintain the training rollers of the rollerassemblies at a substantially uniform height.

Yet another object is the provision of a spreader bar assembly formaintaining the training rollers of roller assemblies in a flexiblestrand conveyor system at a substantially uniform height which isrugged, easy to install, and inexpensive to manufacture,

The invention is illustrated more or less diagrammatically in thefollowing drawings wherein:

FIGURE 1 is a plan view of a portion of a flexible strand conveyorutilizing a spreader bar assembly of the present invention;

FIGURE 2 is an elevation view taken along the line 22 of FIGURE 1; and

FIGURE 3 is a front view of a pair of roller assemblies taken along theline 3-3 of FIGURE 2 showing the relationship of the assembliessuperimposed upon one another.

Like reference numerals refer to like parts throughout the followingdescription.

Referring now to FIGURE 1, a portion of a flexible strand conveyorsystem with the belt omitted for clarity is shown as comprising a pairof ground engaging supports 1, having base or feet 2 adapted to restupon the floor of a mine run or the like. A vertical support stand whichmay or may not be adjustable is indicated at 4 and a rigid cross member5 maintains the support stands in spaced relationship. A return rollerassembly is indicated generally at 6 for supporting the conveying belton its return reach. A pair of U-shaped members 7 and 8 are secured tothe top of the vertical support stand 4 and form support or suspensionpoints for a pair of flexible strands 9 and it? received therein. Anysuitable means may be employed to clamp the flexible strands to thesupport members 7 and 8. The vertical support stands may be so designedthat the vertical members 4 will rock in order to compensate for thestresses placed upon the support stands by the approach and retreat of aload to the stand.

=Next adjacent the ground engaging support structure 1 is an upperroller assembly A including a primary center belt training roller 12pivotally connected at its ends to wing rollers 15 and 16. The wingrollers in turn are connected at their outer ends as at 17 and 18 bysuitable clamps or other means to the flexible strands 9 and 10.

Spaced downstream in the direction of the arrow from the first rollerassembly in FIGURE 1 is a second lower roller assembly B consisting of aprimary belt training center roller 12' pivotally connected to end orwing rollers 15 and 16'. The outer ends of the wing rollers are in turnconnected to flexible strands 9 and 10 as at 17 and 18. While thedetails of the roller assemblies utilized may vary widely it will beunderstood that in any particular conveyor system, the roller assemblieswill be identical.

Located further downstream as viewed in FIGURE 1 is a spreader barassembly 2t). The spreader bar assembly includes an elongatedsubstantially rigid body having a dished central portion 22, see FIGURE2, integrally and rigidly connected to end or flank portions 23 and 24.These flank portions terminate in attaching means 25 and 26 which areadapted to receive the flexible strands 9 and 10 and may be securedthereto by any suitable means,

The distance between the attaching means 25 and 26 of the spreader baris somewhat longer than the distance between the support points 7 and 8at the ground engaging support structure.

Referring now specifically to FIGURE 2, the ground level is indicated at3. A conveyor belt having an upper conveying reach 30 and a lower returnreach 31 is shown in outline supported upon the roller assemblies andthe return roller respectively.

Since the downward sag of the strands'will be at a maximum at a pointsubstantially midway between the ground engaging supports, thecenter-training roller 12 of the lower roller assembly B will besubstantially lower than the primary training roller 12 of the upperroller assembly A. In a conventional 48 inch conveyor assembly thediflerence in height between rollers 12' and 12 may be on the'order ofone inch. By interposing the elongated spreader bar 29, the primarytraining roller 12' of lower assembly B is brought'up substantially tothe level of the primary training roller 12 of upper assembly A. Theamount of overhang required is not great, and in a 48 inch installationa spreader bar having 'a two inch overhang on each side is suflicient tolevel out the rollers.

This effect is best illustrated in FIGURE 3 wherein the position oflower roller assembly B has been superimposed upon that of upper rollerassembly A looking in the direction of the arrows 33 of FIGURE 2. Theoutline of the center rollers 12 and 12' fall substantially upon oneanother whereas the outlines of the wing rollers are displaced withrespect to one another, the wing roller of upper assembly A beingpositioned slightly upwardly from the wing rollers of lower assembly B.The distance between the attaching points 17' and 18 will be somewhatgreater than that between 17 and 18 because the lower assembly B issubstantially closer to the spreader bar than the upper assembly A.

Another important advantage of the invention is the fact that the belttraining effect is improved under all load conditions. For example,conveyor belt conventionally used in conveying installation-s such ascoal mines and the like are usually made of rubber with either a plasticor metal core. Although sufiiciently flexible to form a trough, theyhave a certain amount of inherent stifiness which causes a bridgingeflect when the belt is supported at two relativelyicloselyspacedsupport points vertically offset from one another. Two such pointswould be represented for example by the wing and center rollers of aroller assembly of the present invention. Directly over the pivot pointbetween the rollers, a portion of the belt will be unsupported and hencereceives no training effect. The greater the included angle between thewing roller and the center roller, the greater the unsupported span ofbelt will be. In a 48 inch conveyor for example, utilizing aconventional rubber reinforced helt and a 52 inch spreader bar, theincluded angle at the upper roller assembly A may be on the order of 24and the length of contact between the belt and the centering roller 12may be on the order of 6% inches. In the same installation the includedangle at the lower roller assembly B will be approximately 18 and thelength of contact between the belt and centering roller 12' will beapproximately 8% inches.

Although a preferred embodiment of the invention has been shown anddescribed it should be understood that the invention is not limited tothe specific details here disclosed. For example, although the spreaderbar assembly 20 has been shown as being downwardly concave to clear thebottom of the belt it might be ent rely feasible, especially ininstallations in which the material to be conveyed will always be at auniform depth such as slurries, to reverse the spreader bar so that inefiect it forms an arch under which the belt passes. This may beparticularly advantageous in installations wherein there is plenty ofhead room but small clearance between the bottom of the rollerassembliesand the ground or other protruding objects. Similarly,although the attaching means 25 and 26 have been shown as integral withthe spreader bar 20, it may be advantageous to make them adjustable tothereby vary the length of the bar. Accordingly, the invention should belimited only by the scope of the following appended claims.

I claim:

1. A flexible strand conveyor system including a pair of generallyparallel flexible strands trained along a mine run or the like, aplurality of support structures located at intervals along the strands,the strands being suspended from the support structures, a plurality ofroller assemblies carried by the strands between adjacent supportstructures, said asesmblies having at least a primary training rollerfor carrying a flexible moving belt, and a flexible strand catenary sagcompensating sperader bar for elevating the primary training roller of afirst roller assembly to substantially the level of the primary trainingroller of a second roller assembly, said second roller assembly beinglocated nearer a support structure than the first roller assembly, saidbar being longer between the points at which it engages theflexiblestrands than the distance between the flexible strands at thesupport structures, said bar having a concave shape to thereby clear abelt traveling over the assemblies in all conditions of load.

2. A flexible strand conveyor system including a pair of generallyparallel flexible strands trained along'a mine run or the like, aplurality of support structures located at intervals along the strands,the strands being suspended from the support structures, a plurality ofroller assemblies carried by the strands, said assemblies having atleast a primary training roller for carrying a flexible moving belt, anda flexible strand catenary sag compensating spreader bar for elevatingthe primary training roller of a first roller assembly to substantiallythe level of the primary training roller of a second roller assembly,said second roller assembly being located nearer a support structurethan the first roller assembly, said bar being longer between the pointsat which it engages the flexible strands than the distance between theflexible strands at the support structures, said bar having a concaveshape to thereby clear a belt traveling over the assemblies in allconditions of load.

3. The flexible strand conveyor system of claim 2 further characterizedin that there are four roller assemblies located between adjacentsupport structures, the interval between adjacent roller assembliesbeing substantially equal, said bar being secured to the flexiblestrands between the middle two roller assemblies.

References Cited in the file of this patent UNITED STATES PATENTS 93,361Smith Aug. 3, 1869 1,412,575 Sessoms Apr. 11, 1922 2,773,257 Craggs etal. Dec. 4, 1956 2,851,151 McCallum Sept. 9, 1358 2,875,886 Lo Presti eta1 Mar. 3, 1959

